# -*- coding:utf-8 -*-

class Animal(object):
    def run(self):
        print 'Animal is running...'

class Dog(Animal):
    def run(self):
        print 'Dog is running...'

class Cat(Animal):
    def run(self):
        print 'Cat is running...'

def run_twice(animal):
    animal.run()
    animal.run()

